Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
H, W = tuple(map(int, input().split()))
s = [input() for _ in range(H)]
q = [(0, 0, 0)]
h = {(0, 0)}
opt = float('inf')
while q:
    i, j, k = q.pop(0)
    if i == H - 1 and j == W - 1:
        opt = k
        break
    a = [(u, v)
         for u, v in ((i + 1, j), (i, j + 1), (i - 1, j), (i, j - 1))
         if 0 <= u < H and 0 <= v < W and s[u][v] == '.' and (u, v) not in h]
    q += [(u, v, k + 1) for u, v in a]
    h |= set(a)
print(max(-1, sum(t.count('.') for t in s) - opt - 1))